In a case-sensitive thesaurus, terms (words and phrases) are stored exactly as entered. For example, if a term is entered in mixed-case (using either the CTX_THES package or a thesaurus load file), the thesaurus stores the entry in mixed-case.
To take full advantage of query expansions that result from a case-sensitive thesaurus, your index must also be case-sensitive.
When loading a thesaurus, you can specify that the thesaurus be loaded case-sensitive using the -thescase parameter.
When creating a thesaurus with either CTX_THES.CREATE_THESAURUS or CTX_THES.IMPORT_THESAURUS, you can specify that the thesaurus created be case-sensitive.
In addition, when a case-sensitive thesaurus is specified in a query, the thesaurus lookup uses the query terms exactly as entered in the query. Therefore, queries that use case-sensitive thesauruses allow for a higher level of precision in the query expansion, which helps lookup when and only when you have a case-sensitive index.
For example, a case-sensitive thesaurus is created with different entries for the distinct meanings of the terms Turkey (the country) and turkey (the type of bird). Using the thesaurus, a query for Turkey expands to include only the entries associated with Turkey.